1. Field of the Invention
The present invention relates to immunoassays and immunoassay techniques for the detection of bindable substances, such as antibodies and antigens, and in particular to improved lyophilized reactant mixtures for use therewith. More particularly, the invention relates to improved materials and methodology for use in connection with either the ELISA procedures and materials disclosed in said '656 application, filed Nov. 21, 1988, or the metal sol capture immunoassay procedures and kits disclosed in co-assigned and co-pending U.S. application, Ser. No. 105,285, filed Oct. 7, 1987 (now U.S. Pat. No. 4,859,612). and Ser. No. 177,114, filed Apr. 4, 1988. The entireties of the disclosures of the '285 and '114 applications are also hereby specifically incorporated by reference. Additionally, the disclosure of the '285 application provides an excellent description of prior developments in the field of diagnostic procedures based on immunochemistry and reactions.
2. Description of Prior Activities and Developments
In accordance with certain specific procedures disclosed in said '285 application and in said '114 application, antibody-gold sol particle conjugates and antibody-solid phase particle conjugates are dispersed together in an aqueous system containing human urine. In accordance with certain specific procedures disclosed in said '656 application, of which the present application is a Continuation-In-Part application, antibody-enzyme conjugates are dispersed in an aqueous system containing human urine. When such materials are to be utilized for testing at a place or time that is remote from the place or time where the reactants are prepared, suitable methodology must be employed to ensure the preservation of the reactants and the physical retention of the characteristics thereof which permit the same to be readily dispersed in an aqueous system, particularly one which is made up predominately of human urine.
Lyophilization, or freeze drying as the procedure may be more commonly known, may be used to preserve the ingredients and components for use in procedures such as those which are utilized in the conduct of immunoassays. It is important, however, that the lyophilization procedure results in a homogenous distribution of the components of a multi-component mixture and that the lyophilized mixture remains homogenous and in a readily utilizable form during the storage period. In particular it is important that the lyophilized, solid state materials are readily dispersible upon contact with the test materials to immediately produce a solution and/or dispersion wherein the various components and ingredients are essentially either in solution or in a monodispersed condition.
As described in said '656 application, it is sometimes advantageous to conduct an immunoassay procedure in the presence of binding enhancing agents to enhance formation of an immune complex and/or surfactants (or detergents) which operate to suppress non-specific interactions. Generally speaking, the binding enhancing agents and the surfactants comprise organic materials that are liquid at room temperature, and such materials should, for optimum benefits, be dispersed generally homogeneously throughout the reaction system.
As indicated above, lyophilized materials are often utilized in connection with immunoassay materials to preserve and protect the components, particularly during storage for long periods of time. And it is desirable that a single lyophilized mixture of materials be provided and which is readily dispersible in aqueous solution to supply all of the ingredients which desirably are present in the reaction system during the immunoassay period. However, it has been determined that liquid organic materials which enhance the performance of assays by performing as binding enhancing agents or as surfactants which suppress non-specific interactions are not readily incorporatable into lyophilized mixtures of materials because of their tendency to agglomerate at room temperature and disrupt the homogeneity of the lyophilized mixture. Such normally liquid organic components tend to agglomerate at room temperature to form liquid globules that not only interfere with the shelf life of the lyophilized mixture but prevent the redistribution of the lyophilized ingredients into an aqueous system when the time for conducting the immunoassay procedure has come. Accordingly, in the past it has been difficult to provide kits which include a single lyophilized mixture of materials which, upon reconstitution in an aqueous medium, supplies all of the materials which are desirably present in the reaction milieu.